Could you please check if any other pending task is running in ePO console, Sometimes ePO will not allow other task to terminate if other in-progress is present in server task log.
Or best option to stop the task is restart ePO services
Currently, there is just one task running. Earlier when I posted, there were a couple tasks still running. With just the one, I am still unable to terminate it. But, I will try your suggestion.
I checked more details on your issue and this is a bug in deployment task in ePO console where Terminate option is grayed out. Now restarting ePO service is only option to stop the deployment task.
Ok. I will bear that mind for the future.
Thank you for the replies.